using System;

    using System.Collections.Generic;

    using System.Linq;

​

    public class Program

    {

        public static void Main()

        {

            var numbers = new List<short>{ 1, 3, 10, 1, 2, 44, 26};

​

            var channel1 = numbers

                .Where((n, i) => i % 2 == 0)

                .SelectMany(n => new List<short> { n, n })

                .ToList();

​

            var channel0 = numbers

                .Where((n, i) => i % 2 == 1)

                .SelectMany(n => new List<short> { n, n })

                .ToList();

​

            Console.WriteLine(string.Join(",", channel0.Select(s => s.ToString())));

            Console.WriteLine(string.Join(",", channel1.Select(s => s.ToString())));

​

        }

    }